City University of Hong Kong Department Name



Solar utilization


The solar panels for general applications are fixed in position. The use of the best orientation (surface azimuth angle) and angle of tilt is important for maximizing the energy performance. An optimum tilt angle (or slope) is usually quoted as the local latitude 15o. With the main axis of the panel surface lies on the meridian, i.e. its normal pointing to the south (or the north), the tilt angle should be adjusted towards the equator (positive) in winter and towards the pole (negative) in summer. While this recommendation can be useful as a simple rule of thumb, investigations should be made at specific geographical regions to optimize the solar system performance and to maximize the long-term cost benefit. For the case of Hong Kong and Macau, the sun position is shifted to the north between the 4th of June and the 9th of July. Within this 36-day period, it is the north facade rather than the south façade that will receive direct solar radiation. This bears the implication that for a low-latitude region in the northern hemisphere, a South-facing wall may not receive the highest solar radiation over a year. Simulation studies to evaluate the best positions of the solar panels in region close to Hong Kong (the South China region) were performed.


Variation of annual solar irradiation in Macau with orientation for different tilt angles.


Annual-averaged solar radiation at different daily hours from Macau TMY data


Variations of solar altitude and solar azimuth angles with local time and year day number in Hong Kong


Related publications :


Book chapter:

Chow TT. Solar energy for building applications in the warm Asia Pacific region. In: Trends in Solar Energy Research, Chapter 4, Nova Science Publishers, ISBN: 1-59454-866-8, 2006, pp.77-106.

Journal articles:

Chow TT, Chan ALS. Numerical study of desirable solar collector orientations at coastal region of South China. Applied Energy, 79(3), 2004, 249-260.

Chow TT, Chan ALS, Fong KF, Lin Z. Hong Kong solar radiation on building facades evaluated by numerical models. Applied Thermal Engineering, 25(13), 2005, 1908-1921.

Conference papers:

Chow TT, Fong KF, Chan ALS, Lin Z. Evaluation of solar radiation on vertical walls of buildings in Hong Kong. Proceedings of 2004 Asia-Pacific Conference of International Solar Energy Society, Gwangju, Korea, October 2004, pp.921-926.

Chow TT, Fong KF, Chan ALS, Lin Z, He W. Measured Vs modeled data of solar radiation on building facades of Hong Kong. Proceedings of Healthy Buildings 2006, the 8th International Conference, Lisboa, Portugal, Jun 2006, Vol.III, pp.117-120.

Chow TT, Lu YL, Li CY, Bai Y. Numerical analysis of the integrative performance of a water-flow window system. Proceedings of CLIMA 2013 Congress – 11th REHVA World Congress and the 8th International Conference on Indoor Air Quality, Ventilation and Energy Conservation in Buildings, Prague, Czech Republic, 16-19 June 2013. (CD-ROM)


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